摘要 : Tracking carbon (C) flow through ecosystems requires quantification of myriad biophysical processes,including C routing through microbial and metazoan food webs.Yet detailed organic matter budgets are rarely combined with simultan... 展开 Tracking carbon (C) flow through ecosystems requires quantification of myriad biophysical processes,including C routing through microbial and metazoan food webs.Yet detailed organic matter budgets are rarely combined with simultaneous measurement of C flows supporting microbial and animal production.Here,we synthesize concurrent data sets on organic matter,microbes,and macroinvertebrates from two detritus-based stream ecosystems,one of which was subject to experimental nitrogen (N) and phosphorus (P) enrichment.Our synthesis provides new insights into C flow through forest stream ecosystems.Over 3 yr,the reference stream showed a striking balance of inputs and outputs,with a mean surplus of only 7 g C·m~(-2)·yr~(-1) (~1% of annual inputs),presumably stored in sediments as fine particulate organic matter (FPOM).In contrast,N and P enrichment over 2 yr resulted in severe deficits of C (-576 g C·m~(-2)·yr~(-1) or ~170% of annual inputs),a shortfall presumably met by stored C.Our data set provides an ecosystem-based estimate of the fate of forest litter C at ambient nutrient concentrations:6.2% was leached as dissolved organic C,40.6% and 8.5% flowed to litter-associated fungi and bacteria,respectively,7.5% was consumed by macroinvertebrates,1.8% was exported as coarse particles,and the remainder (35.4%) was presumably fragmented by biophysical processes.Our calculations also allowed an estimate of inputs into the heterogeneous FPOM pool,which is otherwise difficult to obtain.At naturally low nutrient concentrations,50.7% was derived from fragmented litter,39.1% from microbial biomass (mostly fungal),and 10.2% from macroinvertebrate egesta.Nutrient addition drove large changes in C fluxes in the experimental stream,especially in flows of leaf litter to fungi (×1.7 pretreatment) and macroinvertebrates (×2.7),and of FPOM to hydrologic export (×2.6).Our results underscore the key roles of both microbes and metazoans in controlling C flow through detritusbased ecosys 收起